Temperature for Vegetable Seed Germination

Temperature is an important factor of soil conditions to consider when planting vegetable seeds. Without proper temperatures, seeds will fail to germinate or will germinate poorly. Soil temperature should be taken by inserting a soil thermometer 3 to 4 inches into the ground.

Optimal Range

• The optimal germination temperature range for most vegetable seeds falls between 75 to 95 degrees Fahrenheit. Some vegetables' optimal temperatures are on the lower side, such as onions, lettuce, and parsley, while other vegetables are on the higher end, such as corn, cucumbers and summer squash.

Minimum Temperature

• The minimum germination temperature for most vegetable seeds is between 40 to 60 degrees Fahrenheit. Some vegetables, such as peppers and beans, require at least 60 degrees Fahrenheit. A few vegetables, such as onion and lettuce, can tolerate minimum temperatures as low as 35 degrees Fahrenheit.

Maximum Temperature

• The maximum germination temperature for most vegetable seeds is from 85 to 100 degrees Fahrenheit. Some vegetable seeds, such as corn and cucumber, can tolerate temperatures above 100 degrees Fahrenheit. Generally, the optimal temperature is about 15 degrees less than the maximum temperature.